The present invention relates to a process of boring sites in the presence of liquids; particularly for the formation of foundations; of mineral prospectings, etc., the boring being done by a rotating tool as well as by a gripping tool.
Boring in the presence of liquids includes all boring conducted in aqueous sites and/or in dry sites but with the introduction of fluids such as bentonite muds, chemical compounds, grout, etc. The process according to the invention comprises, in its general aspect, separating, in the course of the boring operation, the excavated material and the surrounding liquids by storing the excavated material in an interior volume provided on the interior of the tool and by permitting a controlled circulation of the liquids outside of the interior volume in a reserve volume for the excavated material.
Thus, during the boring operation itself, one assures the circulation of the liquids towards the lower portion of the excavation created and more particularly in such a fashion that the face being excavated is continually and conveniently lubricated.
Likewise, during the descent and raising of the boring tool before and after the boring operation itself, one promotes according to the invention respectively the raising of the liquids towards the top of the excavation or the descent of the liquids towards the end of the excavation thus avoiding the piston effect caused by the displacement of the tool.
According to a preferred aspect of the invention, the circulation of the liquids occurs in a volume provided between the tool and the lateral wall of the excavation.
Furthermore, one preferably assures a forced circulation of the liquids in the reserve volume which is reserved for them.
In the particular instance where the boring is created by virtue of a turning tool, at least during the boring operation itself, one creates the circulation of the liquids towards the bottom by guiding them along a substantially descending helicoidal trajectory.
Furthermore, during the descent of the tool before the boring operation itself, one causes, by virtue of the displacement of the tool, a circulation of the liquids towards the top, in the opposite direction of the displacement of the tool and preferably along a substantially ascending helicoidal trajectory.
Conversely, during the raising of the tool after the boring operation itself, the circulation of the liquids towards the bottom is caused, by virtue of displacement of the tool, in the opposite direction of the latter along a substantially descending helicoidal trajectory.
The invention relates equally to a boring tool adapted in a fashion so as to make possible to perform the above process and comprising at least
a container defining a closed interior volume, this container being provided with retainer means permitting the introduction of the excavated materials in the interior volume while forbidding their exit,
emptying means for evacuation of the interior volume of the container which is controlled by a voluntary control system,
at least one cutting element which, at least in the boring position, projects to the exterior of the container in a fashion so as to result in an excavation having transverse dimensions greater then the tranverse dimensions of the container,
and circulating means for circulating, during the boring operation, the liquids found in the excavation, outside of the volume of the container reserved for the excavated material.
Advantageously, the means assuring the circulation of the liquids are provided with a reserve volume between the walls of the excavation and the lateral wall adjacent to the container of the tool which defines the volume reserved for the excavated material, this volume reserved for the liquids being, according to one preferred embodiment, arranged in a fashion so as to permit a circulation of the liquid such that the liquid assures a constant lubrication of the working elements of the tool without them having damaging effects during the displacement of the tool particularly during the lowering and raising, the controlled circulation of the liquid completely avoiding any piston affect during the excavation.
Applicant has been able to determine that to obtain the desired effects, the ratio between the transverse section of the interior volume reserved for the excavated material and the transverse section of the exterior volume reserved for the circulation of the fluids has to be between 2 and 3 in current boring conditions.
According to an advantageous embodiment of the invention, the lateral external wall of the tool can be equipped with protrusions, in the form of blades for example, extending towards the exterior and substantially perpendicularly to said wall. Naturally, the width of these projections will be less than or at most equal to the width of the cutting element.
Furthermore the blades will preferably have a slope, that is they form an angle other than 90 degrees with the generator line surfaces of the tool container. According to a preferred but not limiting embodiment, the blades, continuous or discontinuous, will surround the container along its entire periphery while providing between them, in the direction towards the top of the tool, guiding means in the form of guiding passages for the liquid going around the container.
In the case where the container of the tool is of a generally cylindrical shape, the blades will be helices or portions of helices wound around the container.
If the tool is rotated during the boring operation itself, the pitches of the helices are oriented opposite to the direction of rotation of the tool such that the liquids, during boring, are guided towards the bottom of the excavation, so as to lubricate the working portions of the tool. One thus achieves a forced guidance of the liquids.
According to another aspect of the invention, the cutting elements comprise at least two knives attached laterally of the exterior of the container of the tool and adjacent to its working end, an opening provided in the container being associated with each of the knives and being equipped with a pivotable door or gate which disengages the opening when a pressure exerts itself on it from the exterior towards the interior of the container and which, on the contrary, blocks it when the pressure exerts itself in the opposite direction. Furthermore, the working end of the tool is constituted by a rocking door allowing for the evacuation of the interior volume of the container, this door being locked in closed position by a latch carried by the container, this latch being controlled by a mechanical system making possible its opening and being drawn back into locked position by an elastic system.